Hfuss^ca, 



Variega. 



tus. 



I.aevila- 

 i»ium. 



84. Oeo- 



PHlLUS. 



ElectWcus. 



C II U S T A C 



Inhabits Europe ; is not very uncommon in many 

 parts of England and Ireland, but has not yet occurred 

 in Scotland or Wales. 



Sp. 2. Variegatus. The whole under lip slightly 

 punctulated with impressed clots ; feet pale-testaceous- 

 yellow, spotted with blackish-brown, or fuscous. 



Lithobius variegatus. Leach's MSS. 



Discovered in Devonshire by Mr Leach, who was 

 rather doubtful whether it is more than a variety of 

 LiTHonivsJo'f catus, but is now confident of its being 

 distinct. 



Sp. 3. Leevild&rvm. Under lip very smooth, with 

 lightly impressed obscure dots on the anterior part; 

 feet testaceous yellow. 



Lit nonius lavilabrum, Leach's MSS. 



Common in Scotland in rocky places, living under 

 stones, in fissures of rocks, and under moss. 



Genus LXXXIV. Geopiiilus. Antennae filiform, 

 composed of fourteen nearly eOjUal joints. 



Sp. 1. Eleclricus. Body linear and yellowish; feet 

 about 140, (144 Latreille.) 



Scolopendra elcctrica, Linne, Fabricius, Latreille ; 

 Geophilus electricus, Leach's MSS. 



Inhabits Europe. 



This curious animal is found on decayed trees : it 

 emits a dim phosphoric light as it moves along, often 

 leaving behind it a shining track. 



O/jsa vn t ion. Besides the species of this family which 

 have been here described, are many more inhabiting 



EOLOGY. 



4G<J 



this country, but their natural history is so imperfectly Crustacea. 



understood, that we cannot at this time venture a de- "•""v-**' 



sorption, lest we fall into error ; much remains to be 



done, but should any species be accurately defined, we 



shall insert it under its proper head, together with all 



new discoveries in this and other classes, In the article 



Zoology. 



Directions for preserving Crustacea for Cabinets. 



Those species which inhabit the sea, should be suf- 

 fered to remain for some hours in cold fresh water to 

 extract the salt, which would soon destroy them by 

 attracting moisture ; they are then to be placed in a 

 crawling posture, and the parts of the mouth are to be 

 displayed by means of pins, until dry : they will then 

 remain in that position. The more minute species 

 must be dried, and afterwards stuck on paper with 

 gum water, in different positions. Those of- the last 

 order, Miriapoda, are to be killed by immersion in spi- 

 rits, and afterwards stuck with a pin on the right side. 

 Crustacea are kept in a cabinet lined with cork, to 

 which they are affixed by pins ; or in boxes loose : the 

 former method is best, as they can then be moved from 

 one place to another without trouble or risk. For a 

 more particular account, we must refer to the article 

 Entomology, where cabinets, modes of preparation, &c. 

 will be found accurately detailed at full length. 



Class II. ARACHNIDES. 



del'"'" e n °^ "J"*""' a s P i(ier > a,K l «'*oj, resemblance ; a class 

 s mm ^ v J^ of amraais proposed as a distinct class by the celebrated 

 Lamarck, Professor of Zoology in Paris, and establish- 

 ed as such by Latredle and other eminent naturalists. 

 As we mentioned in our introduction to this article, 

 the animals composing this class were placed among 

 Insects (Insecta) by Linne, Fabricius, De Geer, and 

 others ; and in this light they were viewed by Latreille 

 in his work on the genera of insects and Crustacea; and 

 he seems to have admitted them as a distinct class in 

 his last work, rather through the persuasion of others 

 than from his own judgment.* 



In considering the classes Crustacea and Arach- 

 nides, we have, at the suggestion of Mr Leach, adopt- 

 ed an arrangement proposed by him, which contains 

 some essential alterations, which, however, seem suffi- 

 ciently warranted, as they tend to the ease of the stu- 

 dent, and so far may prove much to the advancement 

 of the science. By his arrangements, (which we have 

 fully stated in our general remarks in the introduction 

 to this article,) all those animals formerly considered as 

 insects, without wings and antennae, are placed in the 

 class Arachnides; consequently, the orders, 1. Tctra- 

 cera, 2. Myriapoda, 3. Thysanoura, and 4. Parasita 

 of Latreille, are rejected from this class : The two first 

 are placed with the Crustacea, and are considered as 

 one order, to which the name Myriapoda is applied ; 

 the two latter he arranges with Insects, and places 



kiTi" 1 an ° rder caUed h y Uim& A Ptera. Of this we 

 shall have occasion to speak more fully when consider- 

 ing the class Insecta, under the article Entomology, 

 and again comparatively in the article Zoology ; it will 



therefore be unnecessary to take up the time of the Arachni 

 reader, by saying any more on the subject at present ; Ae». 

 we shall therefore pro-reed to give the characters of the v " 

 class Arachnides, with those of its Tribes, Families, 

 and Genera, after which the individual Species, with 

 their structure and economy. 



Anatomical Character. 



No vertebrae"; heart single ; tracheae t for respiration ; 

 feet for moving the body. 



External Character. 



Feet jointed, eight (rarely six) in number. Stigma- 

 ta, or external openings of the trachea?, visible. Body 

 without wings. No metamorphosis, or scarcely any. 

 No antennae. 



ORDER I. PODOSOM A. 



Body composed of segments, each segment being a 

 continuation of the feet (at least apparently s0.) ; Head 

 distinct. Thorax not distinct from the body. Feet 

 eight in number, each segment bearing one on each 

 side. 



TRIBE I. GNATHONIA. 



Eyes four in number, placed on a tubercle on the ante- 

 rior part of the body. Ovifera one on each side. Man- 

 dibules. 



• See the Introduction to his Considerations 

 t Visible from the external openings. 



VOL. VIL PART IJ. 



SvT VOrdrt naturel des Crustaets, da Arachnides, et des Instctes, 



3 F 



